Single Mode vs Multi Mode in Cleaning Lasers

In industrial production, cleaning is a crucial process. Traditional cleaning methods such as mechanical and chemical cleaning can meet certain production needs but often have issues like low flexibility and environmental pollution. With the advancement of technology, laser cleaning technology has emerged as a new favorite in the cleaning field, thanks to its high efficiency, environmental friendliness, and non-contact characteristics. Among the various types of lasers, single-mode and multi-mode fiber lasers are the most commonly used in cleaning applications. So, what are the differences between them? What are their respective advantages and disadvantages? And what are their suitable application scenarios? This article will unveil all these questions for you.

What Are Single Mode and Multi Mode?

Laser modes generally refer to the energy distribution state of the laser in the plane perpendicular to the propagation direction. There are two main types: single-mode and multi-mode. Single-mode means that the laser only produces one mode of output during operation. The energy intensity gradually weakens from the center to the outer edge, with the energy distribution following a Gaussian curve, and the beam is referred to as the fundamental Gaussian beam. Single-mode lasers have high beam quality, small beam diameter, small divergence angle, and energy distribution that closely matches the ideal Gaussian curve. Additionally, single-mode lasers have excellent focusing properties, producing small focal spots and stable modes. They are particularly suitable for cleaning scenarios where strong removal is required, such as rust removal.

Multi-mode lasers, on the other hand, output a spot formed by multiple modes, with the energy distribution inside the spot being more uniform. The more modes included, the more evenly the energy is distributed, and the beam is referred to as a top-hat beam. Compared to single-mode, multi-mode lasers have lower beam quality, larger divergence angles, and require larger apertures in the optical system for transmission. The focal spot is also larger than that of single-mode lasers. However, multi-mode lasers are more capable of achieving high pulse energy, high peak power, and high average power output. The uniform energy distribution makes them advantageous for cleaning scenarios that require less damage to the material and higher efficiency, such as mold cleaning.

Advantages and Disadvantages of Single-Mode and Multi-Mode Laser Cleaning

Single-mode lasers, due to their good beam quality, small focal spot, and high energy density, are ideal for removing strongly adhered contaminants such as rust. They are also suitable for cleaning thin materials and precision parts that are sensitive to heat input. However, because single-mode lasers concentrate energy too much, they may cause some damage to the substrate material during cleaning.

For scenarios that require no damage to the substrate after cleaning, such as for molds, multi-mode lasers are necessary. Multi-mode lasers have a more uniform energy distribution and higher peak power, allowing for control over the peak power density, which is high enough to remove contaminants but low enough not to damage the substrate. In addition, the larger focal spot of multi-mode lasers generally results in higher cleaning efficiency when compared to single-mode lasers for the same cleaning effect. However, for strongly adhered contaminants, multi-mode laser cleaning may not be as effective.

Application Scenarios of Single-Mode and Multi-Mode Lasers

Based on the advantages and disadvantages of single-mode and multi-mode cleaning lasers, their application scenarios differ accordingly.

Main Applications of Single-Mode Lasers:

• Metal Rust Removal: The high energy density of single-mode lasers makes them an ideal choice for metal rust removal. They can efficiently remove rust from metal surfaces, with higher laser power leading to stronger and more efficient rust removal. LightSource has introduced a 1000W high-power single-mode pulsed laser with QBH output, making it easy to integrate and offering strong cleaning capabilities and high efficiency.
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• Weld Oxide Cleaning: During the welding process, the high temperature can cause the formation of oxides and material residues around the weld, affecting the weld’s quality and appearance. LightSource has introduced 200-500W single-mode lasers that can accurately remove oxides, ensuring the weld’s appearance and quality after cleaning.
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• Precision Part Cleaning: LightSource has introduced 100-200W single-mode lasers with QCS output. These lasers offer strong cleaning capabilities with minimal thermal output, causing little deformation or thermal impact on the material after cleaning.
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Main Applications of Multi-Mode Lasers:

• Mold Cleaning: During use, molds may accumulate residues such as plastic, metal fragments, and dust, which can affect the surface quality of products and lead to defects. Regular mold cleaning helps prevent corrosion and wear, extending the mold’s lifespan. Due to the significant differences between the mold substrate and contaminants, using a top-hat beam can effectively remove contaminants without damaging the mold. LightSource has introduced 500-1000W multi-mode lasers with square spot output, offering high cleaning efficiency without damaging the substrate.
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• Perovskite Solar Cell Edge Cleaning: This involves cleaning the film layer at the edges of thin-film solar cells to create an insulating region, facilitating subsequent packaging. LightSource has introduced the YFPN-1000-GMC-H50-F laser, which provides square spot output with uniform energy distribution and high peak power, allowing for efficient removal of the film layer without damaging the glass.
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• Laser Texturing: Laser texturing of material surfaces can significantly enhance the adhesion of coatings or other materials. Depending on the required surface roughness, LightSource offers multi-mode lasers with single-pulse energies of 5mJ, 15mJ, and 50mJ to ensure efficient texturing while meeting different roughness specifications.
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Conclusion

In conclusion, single-mode and multi-mode cleaning lasers each have their own strengths and weaknesses. Single-mode lasers offer high beam quality, precision, and effectiveness for cleaning strongly adhered contaminants and delicate materials. On the other hand, multi-mode lasers provide higher cleaning efficiency and lower damage to the substrate, making them ideal for large area cleaning and situations where the material must remain undamaged. When choosing between single-mode and multi-mode cleaning lasers, customers should consider their specific needs and application scenarios. Single-mode lasers are suitable for fine parts or strongly adhered contaminants like metal oxide layers and coatings, while multi-mode lasers are better for cleaning larger areas or materials where damage is a concern, such as molds, rust, oil, and thin coatings.

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